A loose coalition of Islamist hackers has defaced several French websites in response to "OpCharlieHebdo," a cyber operation launched by Anonymous hackers late last week after the attacks that killed 12 people at the office of the satirical magazine Charlie Hebdo.

In the last few days, "tens" of hacking groups have started claiming responsibility "for religiously motivated defacements," according to Helmi Noman, a researcher with the Berkman Center at Harvard University and the Citizen Lab at University of Toronto. These defacements seem the latest development in an ongoing online spat between Islamist and pro-Western hacktivists.

"Since the story about Charlie Hebdo broke," Noman told Mashable, "many groups, many of which have no previous activity, have emerged online claiming responsibility for defacing websites in support of prophet Mohammed."

On Monday, a group calling itself the United Islamic Cyber Force claimed to have defaced a series of French websites over the weekend, taunting Anonymous, and calling on other Muslim hackers to join their own cyber operations dubbed "OpFrance."

The group hacked into a series of websites and defaced them replacing the regular content with their logo and an Islamist propaganda message.

One of their latest victims, for example, is panierdelamer.fr, the website of something called the "Sea Basket Federation," an organization that claims to repackage unsold products from fish markets and redistribute them to charities.

But the United Islamic Cyber Force is not the only hacking group defacing apparently random websites.

Another group, which calls itself AnonGhost has also been on a defacing websites spree, according to an online archive that lists hacked websites. AnonGhost has been active at least since 2013, and is reportedly led by a 25-year-old hip hop fan that calls himself Mauritania Attacker.

A Twitter account named Mauritania Attacker also boasted of defacing several websites on Monday.

It's not clear, however, whether AnonGhost and the United Islamic Cyber Force are even separate groups. In a second message posted on the hacked site panierdelamer.fr, which replaced the initial one shown above, the United Islamic Cyber Force also claims to be "anon-ghost," though the message starts out with repeated text, as if the hackers made a copy and paste fail.

FallaGa Team, a Tunisian Islamist hacking group, also joined "OpFrance" with a series of defacements, according to the defaced websites archive.

One of its latest victims was the website of Notepad++, an open source text editor, targeted because it released a "Je suis Charlie edition."

Notepad++ releases a version of their application titled "Je suis Charlie edition" - and gets their website defaced. pic.twitter.com/q3EEpzUWv4

The site has now been restored to normal, but for a while, it displayed a message that bore the same hallmarks of the other group's defacement messages: rambling anti-Western pseudo-religious proclamations — and even emoticons.

FallaGa Team has also been around for a few years. In 2013, Vice interviewed one of its members, who claimed to be a 19-year-old Tunisian hacker.

(Attempts to reach these groups for comment have been unsuccessful.)

Noman noted that in many cases the sites have nothing to do with Charlie Hebdo, or anything related to religion. Security experts told Mashable that it's likely the hackers simply chose easy targets, perhaps even sites that have been defaced before and are vulnerable.

In fact, panierdelamer.fr was hacked last week, according to the defaced websites archive.

"Hello.Im sorry about this we don't have anything with you, we only test the security. !!" read the message posted by the hacker in place of the regular content of the site.

It's likely that these hacking groups don't have very sophisticated skills, according to Pierluigi Paganini, a cybersecurity analyst and editor of Cyber Defense magazine.

"Hacking a site is often a really easy feat, and many tools automate recognition and attack in a disarming way," he told Mashable.

But Paganini, as well as Dlshad Othman, a Syrian hacker and technologist who now lives in D.C, said that these sort of attacks should not be underestimated. By hacking into a website, a hacker could then serve malware to its visitors, Paganini explained.

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